Which of the following cranial nerves can regulate heartbeat?

Options

A. X
B. lX
C. Vlll
D. Vll

Explanation

To determine which cranial nerve regulates heartbeat, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Cranial Nerves**:
- The cranial nerves are numbered from I to XII. The question provides options: 10th, 9th, 8th, and 7th cranial nerves.

2. **Know the Functions of Each Cranial Nerve**:
- The 10th cranial nerve is known as the Vagus nerve.
- The 9th cranial nerve is the Glossopharyngeal nerve, which primarily deals with taste and swallowing.
- The 8th cranial nerve is the Vestibulocochlear nerve, responsible for hearing and balance.
- The 7th cranial nerve is the Facial nerve, which controls facial expressions and taste sensations.

3. **Focus on the Vagus Nerve**:
- The Vagus nerve (10th cranial nerve) is known to have a significant role in regulating the heart rate. It is a mixed nerve containing both sensory and motor fibers.

4. **Understand the Role in the Autonomic Nervous System**:
- The Vagus nerve is part of the parasympathetic nervous system, which is responsible for 'rest and digest' functions, including lowering the heart rate.

5. **Conclusion**:
- Based on the functions of the cranial nerves and their roles in the autonomic nervous system, the correct answer is the 10th cranial nerve, the Vagus nerve.

### Final Answer:
The cranial nerve that can regulate heartbeat is the **10th cranial nerve (Vagus nerve)**.

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